Due to the reaction of amide with acrylate, methods of introducing amino group (such as anionic polymerization) to acrylate without initiating side reactions are few. The method of this invention employs the free radical polymerization technique to synthesis the amino-terminated polyacrylate which give good molecular weight control and low polydispersity. Further hydrolysis of the amino-terminated poly-tert-butyl acrylates under acidic condition offers amino-terminated polyacrylic acids.
A prior, 1993 article in the journal Macromolecules, vol. 26, No. 9, pages 2240-2245 by Shefer, Grodzinsky, Prime and Busnel entitled "Free-Radical Telmerization of tert-Butyl Acrylate in the Presence of Bis(4-aminophenyl) Disulfide as a Useful Route to Amino-Terminated Telomers of Poly(acrylic acid)" employs AIBN as the initiator, which is the same initiator employed in the preferred implementation of this invention and employs the same acid, p-toluenesulfonic acid, for subsequent hydrolization. This invention employs a tert-butyl carbonate (t-Boc) protected aminoethanethiol.
There are several reasons for choice of the t-Boc protected aminoethanethiol as chain transfer reagent. First this compound is very easily prepared and obtained in high purity: The t-Boc group converts the solubility of aminoethanethiol from polar aqueous solvents to various organic solvents, such as toluene, therefore, different monomers can be applied in this reaction. The t-Boc group also decreases the hydrogen abstraction from the amine group in free radical polymerization: The t-Boc group is also easily removed under acidic conditions. An azo compound chosen as free radical initiator is 2,2'-azobis(isobutyronitrile) (AIBN), because it is an efficient source of reactive radicals. This method of preparation requires only laboratory capabilities and may be expanded in volume using only larger, but similarly inexpensive equipment.